Uncovering the orbital order in MgV2O4
ORAL
Abstract
In spinel oxides, AB2O4, the B sites form geometrically frustrated pyrochlore lattices. This suppresses TN and may give rise to exotic macroscopically degenerate classical spin liquid states [1]. Breaking of this degeneracy is typically due to longer-range couplings or lattice distortions.
In vanadium spinels, orbital degeneracy offers another route to degeneracy breaking. Theoretical studies have suggested that orbital order can lift the geometric frustration and two potential ground state orbital ordering (OO) schemes have been presented: real/complex orbital order (ROO/COO). Which of these OOs is consistent with the observed behavior has been the subject of debate [2-4].
This presentation will seek to resolve this question in MgV2O4. Previous studies were unable to reconcile the magnetic behavior with either ROO or COO [4]. I will present neutron scattering results which show signatures of the OO. Using generalized spin-wave theory the spectrum will be modeled and show how the OO lifts the frustration. This proposed OO will be shown to be consistent with the emergence of hysteresis in the diffuse scattering.
[1] Bai et al, PRL 122, 097201 (2019)
[2] Di Matteo, Jackeli and Perkins PRB 72, 020408(R) (2005)
[3] Perkins and Sikora PRB 76, 214434 (2007)
[4] Wheeler et al, PRB 82, 140406(R) (2010)
In vanadium spinels, orbital degeneracy offers another route to degeneracy breaking. Theoretical studies have suggested that orbital order can lift the geometric frustration and two potential ground state orbital ordering (OO) schemes have been presented: real/complex orbital order (ROO/COO). Which of these OOs is consistent with the observed behavior has been the subject of debate [2-4].
This presentation will seek to resolve this question in MgV2O4. Previous studies were unable to reconcile the magnetic behavior with either ROO or COO [4]. I will present neutron scattering results which show signatures of the OO. Using generalized spin-wave theory the spectrum will be modeled and show how the OO lifts the frustration. This proposed OO will be shown to be consistent with the emergence of hysteresis in the diffuse scattering.
[1] Bai et al, PRL 122, 097201 (2019)
[2] Di Matteo, Jackeli and Perkins PRB 72, 020408(R) (2005)
[3] Perkins and Sikora PRB 76, 214434 (2007)
[4] Wheeler et al, PRB 82, 140406(R) (2010)
*This work was supported by the Carnegie Trust for the Universities of Scotland, EPSRC, the STFC, the Jülich Centre for Neutron Science (JCNS) and the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-SC0017752. A portion of this research was supported by the National Science Foundation (NSF) through Enabling Quantum Leap: Convergent Accelerated Discovery Foundries for Quantum Materials Science, Engineering and Information (Q-AMASE-i): Quantum Foundry at UC Santa Barbara (DMR-1906325).
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Publication: Complex Orbital Order and Spin-Orbital Entanglement in MgV2O4 (in preparation).
Presenters
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Harry Lane
- Georgia Institute of Technology
- Univ of Edinburgh